T251066: MediaWiki:Missing-revision should provide link to deleted revision for administrators/T264765: CVE-2023-45364: Users without permission are shown MediaWiki:Missing-revision-permission

All the interfaces tell you, "You can view it." But only administrator can view it.

See T264765

The excerpt from the deletion log is not shown to logged-out users.

This is apparently intentional: https://gerrit.wikimedia.org/g/mediawiki/core/+/965f722117315082d53e0fff53b4532bbc639121/includes/page/Article.php#1487

		# Show delete and move logs if there were any such events.
		# The logging query can DOS the site when bots/crawlers cause 404 floods,
		# so be careful showing this. 404 pages must be cheap as they are hard to cache.

This is apparently intentional: https://gerrit.wikimedia.org/g/mediawiki/core/+/965f722117315082d53e0fff53b4532bbc639121/includes/page/Article.php#1487

		# Show delete and move logs if there were any such events.
		# The logging query can DOS the site when bots/crawlers cause 404 floods,
		# so be careful showing this. 404 pages must be cheap as they are hard to cache.

Oops, indeed. I guess we can live with that, it isn't really the thing that made me report this.

In T345037#9137889, @matmarex wrote:

All the interfaces tell you, "You can view it." But only administrator can view it.

See T264765

The excerpt from the deletion log is not shown to logged-out users.

This is apparently intentional: https://gerrit.wikimirror.net/g/mediawiki/core/+/965f722117315082d53e0fff53b4532bbc639121/includes/page/Article.php#1487

		# Show delete and move logs if there were any such events.
		# The logging query can DOS the site when bots/crawlers cause 404 floods,
		# so be careful showing this. 404 pages must be cheap as they are hard to cache.

Personally I don't think this is well discussed. How much negative performance impact can a logging query be made? Should we also care the performance of noarticletext (note in English Wikipedia ifexist is used in noarticletext which is an expensive parser function)? Can we cache the result somehow?

And I previously filed T204227: Consider showing log excerpt for non-existant pages for anonymous users which proposes to alter (or potentially remove) this behavior. (Future discussion of this should happen there.)